When an engine or other equipment is installed in an aircraft, submarine, or other apparatus, it is necessary to establish numerous electrical connections between such equipment and various controls, gauges, etc. located elsewhere on the apparatus in which it is installed. These electrical connections must be readily disengagable in order to facilitate service or replacement of the equipment. On the other hand, it is essential that the electrical connections do not become disengaged during operation of the apparatus because of vibration, shock, etc.
These requirements were originally fulfilled by means of threaded electrical connectors that were secured by safety wires. However, the use of safety wire-type connectors proved to be time consuming and therefore expensive. Also, the installation of safety wires can be difficult or impossible when the connector is situated in a remote location.
These and other difficulties associated with use of safety wire-type electrical connectors led to the development of various self-locking devices for use with electrical connectors. Such self-locking devices usually include at least two members adapted for threaded engagement to secure the electrical connector in the engaged condition and a detent apparatus for preventing disengagement of the threaded members except in response to a predetermined force. The detenting apparatus may operate either in the radial direction, for example, the devices shown in U.S. Pat. Nos. 3,587,030; 3,594,700; 3,601,764 and 4,109,990, or in the axial direction, for example, the devices shown in U.S. Pat. Nos. 3,069,187; 3,462,727; 3,552,777; 3,594,700; 3,808,580 and French Pat. No. 2,002,273.
The prior art reference which is perhaps the most pertinent to the present invention is Blight et al. U.S. Pat. No. 3,343,852 granted Sept. 26, 1967. In the Blight et al. device a plurality of spring loaded balls engage a gear tooth to provide ratcheting action. This in turn prevents the disengagement of a pair of threaded members which retain mating electrical connectors in the engaged condition.
In the devices disclosed in most of the above-listed patents, the detenting apparatus operates continuously. That is, the detenting apparatus functions throughout the threaded engagement, and throughout the subsequent threaded disengagement, of the members which secure the electrical connectors in engagement with one another. Such continuous detent apparatus operation causes unnecessary resistance to the initial phase of the threaded engagement of the connector securing members.
Another deficiency that has been experienced in prior art self-locking coupling devices adapted for use with electrical connectors (such as Blight et al.) relates to the lack of any structure which provides visual or tactile proof of the fully locked status of the device. Thus, although fully locked status is readily ascertainable both when the electrical connector securing members are being threadedly engaged and when an attempt is made to threadedly disengage the members, nothing is provided in most of the prior art self-locking coupling devices to provide visual or tactile proof of the locked status of the device.
The present invention comprises a self-locking coupling nut which overcomes the foregoing and other difficulties long since associated with the prior art. In accordance with the broader aspects of the invention, electrical connector securing members are maintained in threaded engagement by a plurality of spring loaded balls which engage spaced apart grooves. However, the spring loaded balls do not engage the grooves until the coupling nut is substantially fully engaged. In this manner the initial threaded engagement between the electrical connector securing members is substantially facilitated.
In accordance with another aspect of the invention, the spring loading of the balls is provided by a circular spring extending around and engaging each of the balls. When the electrical connector securing members are disengaged, the circular spring is enclosed within a groove. As the electrical connector securing members become fully engaged and the balls enter the spaced apart grooves to restrain disengagement thereof, the spring is cammed outwardly to a position wherein it extends beyond the slot. The positioning of the spring thus provides visual and tactile proof of the fully locked condition of the coupling nut.